SGR2, a phospholipase-like protein, and ZIG/SGR4, a SNARE, are involved in the shoot gravitropism of Arabidopsis.

In higher plants, the shoot and the root generally show negative and positive gravitropism, respectively. To elucidate the molecular mechanisms involved in gravitropism, we have isolated many shoot gravitropism mutants in Arabidopsis. The sgr2 and zig/sgr4 mutants exhibited abnormal gravitropism in both inflorescence stems and hypocotyls.